Incidence and Associated Factors of Postoperative Pulmonary Complications after Abdominal Surgery in the Public Hospital, Addis Ababa, Ethiopia

Background Postoperative pulmonary complications are a wide variety of disorders that affect normal respiratory functions, which in turn lead to morbidity and mortality. The extent to which it occurs is not yet studied in most clinical settings. This study assessed the incidence and risk factors of postoperative pulmonary complications in patients undergoing abdominal surgery under general anesthesia. Methods A multicenter, prospective cross-sectional study was conducted at Menelik II, Tikur Anbessa Specialized, Zewditu Memorial, and Yekatit 12 Memorial hospitals after obtaining ethical clearance from each hospital. The study recruited a total of 287 participants using systematic random sampling. The data collection tool included sociodemographic, surgical, and anesthetic factors. Participants were followed for 7 days postoperatively, and any respiratory problems were recorded once identified. The collected data were entered and analyzed using SPSS version 26. Both bivariate and multivariate logistic regressions were used for analysis. A p value of <0.05 was considered statistically significant. Results About 33% of the participants that underwent abdominal surgery developed postoperative pulmonary complications. Age > 65 years (AOR = 12.091, 95% CI = 3.310–44.169), duration of surgery >3 hours (AOR = 11.737, 95% CI = 3.621–38.039), preoperative oxygen saturation <94% (AOR = 10.671, 95% CI = 3.794–30.016), and postoperative serum albumin level <3.5 g/dl (p value <0.001) were associated with postoperative pulmonary complications significantly. Conclusion and Recommendations. The incidence of postoperative pulmonary complications after abdominal surgeries was high. Age >65years, duration of surgery >3 hours, preoperative SpO2% <94%, cigarette smoking, and postoperative serum albumin level <3.5 g/dl were factors strongly associated with postoperative pulmonary complications. We recommend special care for elderly patients, limit the surgical duration to less than 3 hours, treat the underlying cause of desaturation, and correct postoperative serum albumin to prevent the occurrence of postoperative pulmonary complications.


Introduction
A postoperative pulmonary complication is a broad term used to describe any adverse changes in the respiratory tract occurring after surgery and affecting the clinical course of the patients. e definitions for PPCs are derived from the European Society of Anesthesiology and the European Society of Intensive Care Medicine [1,2].
Several works of the literature showed a wide variation in the occurrence of postoperative pulmonary complications ranging from 5 to 60% [1,. Variation of definitions, preoperative tests to identify the associated risk, criteria used to diagnose, and diverse populations in different countries were the major contributory factors for developing postoperative pulmonary complications in a wide range [1]. A study conducted in Nigeria revealed that the rate of postoperative pulmonary complications was 52% and another study conducted in Zimbabwe and Ethiopia showed that 42.4% and 21.7% of patients developed postoperative pulmonary complications [4][5][6][7][8].
Knowledge about how PPCs occur, how to identify and treat postoperative pulmonary complications, and what factors contribute to it is lacking in most developing countries. is study hopefully aims in identifying those risk factors and developing strategies to reduce pulmonary complications. Preoperative factors: preoperative anemia, malignancy, renal failure, COPD, asthma, CHF, HTN, DM, and recent respiratory infection.

Methods
Anesthetic and surgical factors: type and duration of surgery, incision site, position, type of anesthesia, SpO2%, muscle relaxants, blood loss, transfusion, and intraoperative complications.

Sample Size and Sampling Technique
e sample size was determined using the single population proportion method. A previously conducted study at Gondar University which reported the incidence of postoperative pulmonary complications as 21.7% [15] was used as a reference for sample size calculation by considering 95% and 5% margin of error.
us, it was computed as follows: (1) Adding a nonresponse rate of 10% gives the final sample size of 287.

Sampling Technique.
A systematic random sampling technique was assigned.

Data Collection
Techniques. Data were collected by using a pretested structured tool. Before the initiation of data collection, training was given to data collectors, and regular supervision was made throughout the collection process. e data collection starts during the preoperative period once informed consent was obtained from study participants. e data collection tool included preoperative demographic data, preoperative comorbidities, intraoperative anesthetic, surgical factors, and postoperative factors. e confidentiality was maintained throughout data collection procedures. All the above factors were recorded once observed by data collectors at any stage of data collection procedures. Patients were followed for seven days by data collectors during the postoperative period, and any new finding that suggested respiratory disorder was observed and confirmed by chest physicians after making full assessments.

Operational Definitions
Postoperative pulmonary complications: the occurrence of 2 or more of the signs and symptoms for at least 2 consecutive days, occurring within 7 days of surgery [12,[16][17][18][19] (i) Abnormal breath sounds: rhonchi/rales/decreased breath sounds (ii) BAL/sputum culture-positive infective cause confirmed (iii) Cough with sputum+ fever (T > 38) (iv) Physicians/nurses' judgment of the respiratory cause (v) Respiratory rate >25/min (vi) Saturation <90% room air, <94% with 100% oxygen for >2 hours (vii) X-ray: consolidation/infiltrates/effusion new findings Abdominal surgery: broadly covers surgical procedures that involve opening the abdomen Postanesthesia care unit: A place where the patient is admitted after surgery and anesthesia to be given by professionals Mobilization is defined as the ability to walk >10 m from the bed [20] 2.7. Data Processing, Analysis, and Interpretation. Data were checked for completeness code and entered into SPSS version 26. Descriptive statistics were computed, and the results were presented as frequency and percentage. A goodness fit test was conducted using the Hosmer and Lemeshow test. Both bivariate and multivariate logistic analyses were used to find out the associated factors. A variable with a p value ≤ of 0.2 from a bivariable was considered as a candidate for multivariate analysis. e strength of association was assessed using an odds ratio with a 95% confidence interval. e findings were presented using tables and graphs. e level of statistical significance was declared at a p value <0.05.

Data Quality Assurance.
To assure the quality of data, training on the objectives and relevance of the study and brief orientations on the assessment tools were provided for data collectors. During data collection, all data were collected and properly filled in the prepared format. e supervisor controlled the data collector and checked for completeness daily after data collection. Daily data curation and cleanup were made by principal investigators.

Ethical Considerations.
Ethical clearance and approval were obtained from the ethical review committee. An official support letter was written to each selected Addis Ababa governmental hospital and permission for data collection was sought from the responsible authorities. e purposes and the importance of the study were explained, and verbal as well as written informed consent was obtained from each participant. Confidentiality was ensured by avoiding personal identification on the questionnaire.

Sociodemographic Variables.
A total of 287 participants were recruited and completed the study. e findings for sociodemographic data are given in Table 1.

Perianesthetic and Surgical Factors.
Various intraoperative anesthesia and surgery-related factors were assessed and the result is given in Table 2.

Postoperative Factors.
e factors that contributed to postoperative pulmonary complications were analyzed and are given in Table 3.

Bivariate Analysis to Identify the Association of Independent Variables with Outcome Variables in Surgical
Patients. Binary logistic regression analysis was conducted to identify the association of the outcome variable with each explanatory variable. Nine independent variables were included in the bivariate analysis. Exclude variables that do not fit for the final model using a p value >0.2 when multivariate analysis was performed. Four variables were selected for the multivariable model, and all of the variables were significant by using p value <0.05 (Table 4).

Multivariate Analysis of Factors Associated with Postoperative Pulmonary Complications in Surgical Patients.
e results of the multivariate analysis are given in Table 5.

Overall Incidences of Postoperative Pulmonary
Complications.
e overall incidence of postoperative pulmonary complications was 33% and is shown in Figure 1.

Types of Pulmonary Problems Observed in Postsurgical
Patients. Among different types of PPCs, pneumonia (50%) and atelectasis (24) were the commonest ones. e graph shows different types of disorders affecting the respiratory system, as shown in Figure 2

Discussion
is study revealed the incidence of postoperative pulmonary complications after abdominal surgeries was 33%. is finding is higher than that of the report of the study conducted at Gondar University Hospital in 2015 [15]. e possible explanation for this could be a larger sample size used in their study, and interobserver variability could have the potential to affect the finding. However, this finding was comparable with the results of the observational analytical study conducted in India by Sinouvassan et al. which came out with an incidence of 34% [21]. Our study's finding was also in line with a retrospective study conducted in Turkey by Diken et al. which showed an incidence of 32.6% [22]. is might be due to the similarity in criteria used to diagnose postoperative pulmonary complications or postoperative follow-up periods.
Meanwhile, the finding of this study was lower than that of the study conducted in Zimbabwe by Tadyanemhandu et al. , Harare, which revealed that 42.4% of study subjects developed postoperative pulmonary complications [3]. Moreover, an observational cohort study conducted in an Australian tertiary hospital by Haines et al. and Parry et al. revealed incidences of 39% and 42%, respectively [23,24]. e differences in the study design may have contributed to this discrepancy in the incidences.
Participants who had postoperative serum albumin levels <3.5 g/ were 23 times more likely to develop postoperative pulmonary complications (p ≤ 0.001). e possible explanation would be albumin is necessarily indicating the nutritional status of the patients, is important for muscle strength, and also promotes the wound healing process. e serum albumin level indicates the   Anesthesiology Research and Practice nutrition status and associated weakness of the expiratory muscles, decreased chest wall expansion, and an increased incidence of pulmonary complications in patients [25]. Age greater than 65 years old was 12 times riskier of postoperative pulmonary complications (p ≤ 0.001, AOR: 12.09, 95% CI: 3.31-44.1). e likely cause could be aging was related to increased cardiorespiratory comorbidities which can be aggravated during surgery and anesthesia [13,26]. Surgical duration longer than 3 hours would be 11 times more likely to have postoperative pulmonary complications (p ≤ 0.001, AOR: 11.7, 95% CI: 3.62-38.03). is finding is in line with different pieces of the literature studied by different researchers abroad [3,12,15]. e possible explanation may be the long duration of surgery was associated with an altered physiological response of metabolic activities [13,25].
Study participants who had preoperative oxygen saturation <94% were 10 times riskier for postoperative

Strength and Limitations of the Study.
e study identified that pulmonary complications can affect a significant number of surgical patients during the postoperative period. It also identified major associated factors that had the potential to contribute to the occurrence of postoperative pulmonary complications. e limitation of the study was that there can be another associated factor, which may contribute to the problem and interobserver variability in diagnosing postoperative pulmonary complications.

Conclusion and Recommendations
e postoperative complication was found to occur significantly in patients undergoing both upper and lower abdominal surgeries. e study revealed age >65 years, duration of surgery >3 hours, SpO 2 % <94%, and the postoperative serum albumin level <3.5 g/dl were factors strongly associated with postoperative pulmonary complications. We recommend the healthcare workers to give a deep insight into the identified factors and take necessary precautions while caring for the patients. A future study with a large sample size and large varieties of surgical specialties is recommended.

ASA:
American Society of Anesthesiologists BMI: Body mass index EPCO: European perioperative clinical outcome ICU: Intensive care unit LOS: Length of hospital stay NRS: Numerical rating scale

Data Availability
e data used to support this study are available from the corresponding author upon request.

Conflicts of Interest
e authors declare that they have no conflicts of interest.